I'm at 170,000 with my m104 I replaced idler pulley 9 month ago from Phil,the best parts.I have slipping belt noise on ocassion,last 5 to 10 seconds.may repeat when at idle.I know the adjuster can go bad,but its near water pump time, an maybe alternator?.Faster easyway to trouble shoot this one.In alway search forum first,could find no help.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

well tensioner is cheaper than a alternator so I'll go with it
I'll report later on it, and try Pelican parts

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

Can youn stop fan at idle when engine is cold? Its hard to use a sethoscope with fan turning

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

Remove belt and spin pulleys. See if one of them is loading belt up. Is compressor on or off when it happens?

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Jim

On M104, best thing to do is slacken the belt and spin all the pulleys.

What I usually did was loosen the P/S pulley enough to slip the belt off. I always hated to touch that belt tensioner. Look at it wrong and it would fail.

Just spin all the pulleys and make sure none are making noise. Non-OEM tensioners don't last very long

Most likely issue is the tensioner.

Of course do you have an OE quality belt as well?

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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Just went through this with my W201. Got a used tensioner pulley and it was worse that the OEM one, which was not my problem afterall. Went ahead and bought new from MB.

Removed the tensioner and inspected it. I've replaced it before, and the OEM one really was bad at the time.

This time, the chirping was from the alternator. I spun the shaft and it growled and gave resistance. A box store wanted $199 for a rebuilt unit. I bought new bearings for my unit, and a regulator, for $44, and did it myself. The hardest part was pressing the bearings on and off of the rotor. Had it back together in 30 minutes, installed on the car in an hour, and no chirping anymore. Still have my OEM unit after 300K. Proud of it.

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My first Mercedes Benz. 4/6/07.

1984 190E (201 024) 2.3L four.

thanks for the tensioner warning

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

If you remove your tensioner, and find lots of cracks in the rubber that you will see on the non-operating side, chances are good that it's worn out.

MB must own patents on a certain kind of rubber. Their rubber parts cost more than anything. (I know... MB is just proud of their parts, and it costs money to keep rubber parts available for our 25+ year old cars!!)

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My first Mercedes Benz. 4/6/07.

1984 190E (201 024) 2.3L four.

If we're talking about the tensioner on a 1999 S320, then that looks like the newer spring style and not the old rubber bushing style. That tensioner will probably last forever.

And if slackening the belt is anything like on my W202, then it's easy. No more lock bolt, no more adjusting rod, no more fragile rubber bushing.

You guys are lucky, I hope. Maybe one day these cars will get old enough for me to be able to aquire one---for now, I'll stay with a moldy oldie.

Best of luck with your squeal!

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My first Mercedes Benz. 4/6/07.

1984 190E (201 024) 2.3L four.

There was a sea change with the W202. What I would call Japanification.

1) Electronic tranny.

2) Japan style AC with electronic controls, ice cold forever (so far untouched in my 2000 C280), and a low drag compressor that the engine barely feels.

3) Spring tensioner.

4) Lighter handling car.

found the problem shiny pulley,on alternator,will rebult my alternator

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt